Japanese Navy air service, 1938-45, with hindsight?

Hi Lancer21,

Problem is the Kinsei engine will drastically reduce the range, as shown by the A6M8 compared to all the other Sakae powered Zeros, plus the fact that it has a diameter of 1,22m compared to 1,15m for Sakae would mean they will have to increase fuselage diameter if they still want the MGs to be in the cowling, which leads to a weight penalty etc.

Is there an accepted (or at least reasonable) set of performance figures for the A6M8 one could use to extrapolate A6M1 performance with the Kasei engine?

Regards,

Henning (HoHun)

There are a couple online sets of specs for the A6M8 that seem consistent, but no idea to what, if any extent, they are quoting each other:
 
The Warthunder link is the best, thanks BB1984.

HoHun, I was basing my data on the japanese wiki article on A6M variants here, which is pretty much the same as the Warthunder link (except the WT has some very interesting drawings and additional data etc.)

So yeah, it looks like the range was halved by putting in the Kinsei on A6M8 from the previous versions. From what i can gather the OTL A6M2 had a maximum radius of 600nm in 1941/42, but all else being equal if you put a 1070HP Kinsei-46 (seems this is the variant considered) on it it will drop to about 300nm? I guess it depends on the fuel consumption of the Kinsei-46 vs Sakae-21. They may perhaps squeeze 400nm out of it by adopting later mods, like increasing the wing tanks from 380 to 420 litres as on A6M3, and by fitting those outboard 45 litre small tanks. But how about things like speed?
 
Come to think about it, Nakajima might've been the best company to make a next-gen fighter to replace the Zero. They were designing the J1N for the role of long-range fighter, that at the end was bought as a recon, and later re-purposed as a night fighter. Under 480 manufactured from mid-1942 to late 1944. They also made the C6N, a fine recon machine, again made in small numbers - under 470. Some were converted in fighters. Nakajima was also making Zero for the Navy (doh).
I'd suggest that Nakajima makes a long-range fighter around the Ha-41 engine for late 1941. Move to Ha 109 from 1942, and to Homare by early 1944. Phase-out the production of the Zero by early 1943, at least what is poduced at Nakajima's factory devoted to the Navy aircraft (other factory was making Army aircraft). The J1N was with self-sealing tanks, so our brave new fighter has to have those, too.

The D4Y (with radial engine from the start) needs to be manufactured in greater numbers, so more can be spared for recon job, and also to replace the Vals by a faster rate. Judy also needs self-sealing tanks.
 
Hi there Tomo,

Sorry i haven't come to play here lately, have some RL things to deal with, but as a bit of a distraction i was going over the IJNAF and IJAAF alternate birds last night. So indeed Nakajima working on an single engine interceptor instead of the J1N is a much better use of their design resources. Incidentally when the J2M troubles became apparent Nakajima offered a variant of the Ki-44 as J2N for the Navy, so your idea has good merit, either a Ki-44 derivative or a clean sheet design flying in 1941/42 would again free Mitsubishi to work on the A7M.

The C6N was a good bird, but actually the Ki-46 (which the IJNAF did use) was faster (refering to the Ki-46-III version with Ha-112-II engine), so why not just build more of those for the navy? Ok it can't land on a carrier but since the C6N was never used on CVs anyway, and this thread implies a bit of hindsight, just go for more Ki-46s, again freeing Nakajima's designers to work on something more useful.

Not sure if i mentioned it before, but also cancelling that totally useless G5N would free Nakajima to design and fly the B6N in 1941, one year early (powered by the 1500HP Kasei or Ha-109). Perhaps the first units might be ready by late 1942, at a time when the B6N would be almost as fast as the F4F, the main USN fighter, it would be much harder to catch (at least for a while) compared to the slow and vulnerable B5N.
 
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Hi there Tomo,

Sorry i haven't come to play here lately, have some RL things to deal with, but as a bit of a distraction i was going over the IJNAF and IJAAF alternate birds last night. So indeed Nakajima working on an single engine interceptor instead of the J1N is a much better use of their design resources. Incidentally when the J2M troubles became apparent Nakajima offered a variant of the Ki-44 as J2N for the Navy, so your idea has good merit, either a Ki-44 derivative or a clean sheet design flying in 1941/42 would again free Mitsubishi to work on the A7M.

Hopefully the things will work out for you :)
IMO - Nakajima might've design a CV-capable long-range fighter sized & shaped like the future Ki-84 or Ki-100, or indeed a big-wing Ki-44? Folding wings, butterfly flaps, self-sealing fuel tanks and back armor from the get-go (as in the J1N), two cannons + 2-4 LMGs for the start.
For the Mitsubishi - make a no-nonsense fighter around the Ha 104 with water-alcohol injection, sorta Japanese Sea Fury? We know that Ha 104 made a lot of power even with 87 oct fuel - the big engines running on low boost have a lot of appeal for the Japanese. If/when the Ha-43 materializes, up-engine the fighter by all means.

BTW - both of these should've been able to double as dive-bombers ASAP.

The C6N was a good bird, but actually the Ki-46 (which the IJNAF did use) was faster ( refering to the Ki-46_III version with ha-112-III engine), so why not juts build more of those for the navy? Ok it can't land on a carrier but since the C6N was never used on CVs anyway, and this thread implies a bit of hindsight, just go for more Ki-46s, again freeing Nakajima's designers to work on something more useful.

IJN and IJA were not friends :) But indeed, the Ki-46 was very good in what it did.
Carrier-borne recon job can be undertaken by a LR fighter outfitted with cameras, as well as by D4Y outfitted with cameras.

BTW and IMO - the earlier P1Y Ginga instead of the G4M? The G4M was the appearance and size of a transport A/C (it was used as one, too), while the P1Y was a much smaller and sleeker job, gaining 70-80 km/h even vs. the fastest G4M versions. Both carried the same (small) bomb load over great distances.

Not sure if i mentioned it before, but also cancelling that totally useless G5N would free Nakajima to design and fly the B6N in 1941, one year early (powered by the 1500HP Kasei or Ha-109). Perhaps the first units might be ready by late 1942, at a time when the B6N would be almost as fast as the F4F, the main USN fighter, it would be much harder to catch (at least for a while) compared to the slow and vulnerable B5N.

Yes, realistically the G5N was a waste of limited resources, even if they managed to make a meaningful number of them - it can't reach USA, impractical for tactical duties, the existing 2-engined bombers (or the ones in the pipeline) can tackle anything in China or Indochina.
B5N needs to be replaced ASAP, whether by an earlier B6N, or by Japanese forgetting their favorite tool - torpedo bomber - and going all-in with dive bombers and fighter-bombers. Having to fly at low altitude, straight and level in the teeth of many, many hundreds of 20mm and 40mm AA guns is not conductive to the health of crews or aircraft they flew... But then, a dive bomber flying at 15000 ft is just where the VT-fused ammo for the 5in gun awaits; granted, it is 1944 for the VT fuse to enter the stage.

OTOH, one cannot help but give a lot of credit to the Japanese aircraft designers, engineers and technicians for the sheer number and variety of relatively trouble-free aircraft they made in short years of 1940-45 (well, not that short for the people on the receiving end of the atrocities). Granted, it didn't help out with economies of the scale required for the all-out war the ww2 was.
 
Agree about the P1Y, even the version with Kasei engines was practically as fast as the F4F. It is also as fast as the J1N, so a night fighter version of it is perfectly reasonable (like the germans did with Ju-88).

However the G4M requirement stipulated a tail cannon, so i was looking at the Ki-67, it's smaller than the G4M and it's 50-60kph faster than the fastest G4M3, with practically same horsepower (2x1900HP Ha-104 vs 2x 1850HP Kasei). So if they still want a tail cannon, they could still make as smaller, faster G4M along the lines of the Ki-67, among other things the G4M was designed for crew comfort and extreme range (so no protected tanks until G4M3), but what's the point of flying your crew in comfort out to 700-800nm only to be massacred at the objective (because your plane is slow and has no protected tanks)?

So at the very least, all the large, valuable and expensive planes like G3M, H6K etc must have protected tanks by 1941, even if the smaller single engined ones still don't.

Sea Fury, now that's something i kinda just realized, the A7M is the closest thing the japanese had to it, except it's larger, especially span! Also looks like the Centaurus is pretty much the same size as the Ha-104, capacity, diameter, weight, everything. So here's the japanese Sea Fury right here, a somewhat smaller A7M (especially a smaller wing is crucial) powered by a Ha-104/MK10 engine! The latest Ha-214 engine was giving 2400HP with MW boost. Never mind matching the Sea Fury speed, or even the F4U-4, if they could make this ATL A7M a roughly 400mph fighter and match the MW boosted F-4U-1s it will still be massive boost for IJNAF.

Same goes for whatever Nakajima will design in this ATL, if they could get a roughly 400mph Shiden-kai equivalent as a land based interceptor (powered by my ATL 18 cylinder 48 litre Mamoru, starting at 1800-1900HP, but late war Ha-219 was doing 2450HP), this will also be a nasty opponent for everything but the latest F4U-4, P-47M/N etc.
 
Regarding the Ki-84 speed, indeed the american figures are too high, iirc in japanese wiki it says the speed of a fully rated Ki-84 was 640-650kph. The lower figure of 624-631 kph might be because the engine was derated (similar to what the germans had to do).

Same discrepance i found for the N1K2-J, iirc the highest figure i saw was 644kph, though i think i also saw 620kph. The usual figure as you know is given as just 595kph, which i always found inexplicably low, but if the engine was derated that makes sense. On the other hand, due to the war situation (poor fuel, poor metals/building quality), how many japanese fighters would have performed to their full potential, especially the 2000HP ones?
Could the differences have been due to the Allies using higher-octane fuel for the testing?
 
Hi Doc,

Regarding the Ki-84 speed, indeed the american figures are too high, iirc in japanese wiki it says the speed of a fully rated Ki-84 was 640-650kph. The lower figure of 624-631 kph might be because the engine was derated (similar to what the germans had to do).

Same discrepance i found for the N1K2-J, iirc the highest figure i saw was 644kph, though i think i also saw 620kph. The usual figure as you know is given as just 595kph, which i always found inexplicably low, but if the engine was derated that makes sense. On the other hand, due to the war situation (poor fuel, poor metals/building quality), how many japanese fighters would have performed to their full potential, especially the 2000HP ones?
Could the differences have been due to the Allies using higher-octane fuel for the testing?

At least with regard to the Ki-84, there's no indication that it was ever tested for performance by the Allies, and the reported speed data is clearly marked as calculated estimate based on minimal data in the original intelligence data sheets:


Regards,

Henning (HoHun)
 

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